st: Questions concerning the xttest2

Dear users,
I tried to use the xttest2 to check for cross-sectional correlation.
Yet, I obtain the error message:
"Correlation matrix of residuals is singular.
not possible with test"
r<131>
The problems seems to be, that the number of households in my samples
is bigger than the number of periodes. But the nember of countries in
my samples is smaller than the number of periods. (N=15, T=17)
Waht is the cause of the problem?
In that case, how can I test for contemporaneous correlation?
And if PCSE analysis ignoring the error message, any problem?
Any help would be greatly appreciated.
Thank you.
Youngmi Kim
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